The present invention relates to a fuel injection system for a gas turbine engine, more particularly such a system which creates a fuel and air premixing zone between the fuel injection sites and a downstream edge of a flameholder.
Fuel injection systems for gas turbine engine combustion chambers are known and typical examples are illustrated in U.S. Pat. No. 5,193,346 and European Patent 0 488 556. These systems comprise first and second fuel injection assemblies which are substantially centered relative to a central axis of the combustion chamber. They also include a flameholder inside the combustion chamber displaced away from the upstream end wall of the chamber. In these known systems, a first fuel injection assembly is located on the central axis and is enclosed by a sleeve extending axially along the axis so as to be coaxial therewith and a second fuel injection assembly which is located axially downstream of the sleeve along the axis. The second fuel injection assembly is axially offset from the transverse downstream end of the sleeve which is furtherest from the upstream end wall of the combustion chamber. The second fuel injection assembly is located between the transverse end of the sleeve and the upstream end wall of the combustion chamber.
The known fuel injection systems do not permit the stabilization of the combustion in the immediate vicinity of the upstream end of the combustion chamber and, as a result, do not satisfactorily reduce the emission of nitrogen oxides (NO.sub.x) nor do they allow the homogenizing of the local fuel/air mixture richness.